Airbags were developed to protect occupants of cars during vehicle crashes. Originally airbags were viewed as an alternative to seat belts, because they are passive devices which do not require the cooperation of the car's occupants to be effective. However, experience has shown that airbags should be considered an adjunct to seat belts. When used properly, airbags can in certain crash situations reduce injuries to occupant. An airbag is a gas-filled bag which is rapidly deployed in the event of a vehicle crash. When appropriate crash sensors determine that a crash has occurred, the airbag is rapidly inflated to create an impact cushion between the occupant(s) of a vehicle and the structure of the vehicle. Consideration is also being given to the design of airbags which better position the vehicle occupant(s) to withstand crash-induced accelerations.
An airbag system is made up of two basic functional components: the airbag module, including the means for deploying the airbag; and the sensors and circuitry which determine whether the airbag should be deployed.
Recently sensors have been developed to determine the weight imposed on the front seat, and the value of the determined weight may then be used as an input into the system logic which determines whether or not an airbag should be deployed or whether the mode of deployment should be modified in airbag systems which are capable of varying the deployment sequence to accommodate varying circumstances. In some cases, however, these weight sensors can be confused by loads imposed by the compression of the seat resulting from installing a child's car seat and tensioning the seat belt to hold the child seat into place.
One proposed solution is to place a device on each child seat which can be detected by a sensor and thus used to determine the presence of a child seat. However, this approach relies on gaining cooperation of all manufacturers of child car seats and it would take many years before all old child car seats would be replaced with child car seats containing the needed sensor. What is needed is a sensor which can provide data for determining whether a child's car seat is positioned in the front passenger seat of an automobile.